The search for new antibiotics produced by soil microorganisms has encompassed the screening of various genera of bacteria, high bacteria and fungi including many strains within each species.
Among the microorganisms that have not received much attention is a fungus which belongs to the form class Deuteromycetes (or Fungi Imperfecti), form order Sphaeropsidales, form family Sphaeropsidaceae and the form genus Cytospora sp. W.F.P.L. (Western Forest Products Laboratory in Vancover, B.C., Canada) 13A.
While screening for new antibiotics from plant pathogenic fungi strong antimicrobial activity was observed in agar plate cultures of at least ten genera of fungi not previously reported to produce any antibiotics.
U.S. Pat. No. 3,151,038 to Gray describes a process for the production of proteins and while Cytospora sp. is mentioned there is no reference to Cytospora sp. W.F.P.L. 13A and the process conditions employed are significantly different.
MacMillian et al, J.C.S. Perkin 1, 14, 1487-1493 (1973) describe colletoketol, which appears to be a stereoisomer of Grahamimycin A, produced herein. Colletoketol was produced by the fermentation of the plant pathogen, Colletotrichum capsici.